License Agreements (Details) $ in Thousands, € in Millions	1 Months Ended							3 Months Ended	7 Months Ended	12 Months Ended					115 Months Ended	150 Months Ended
	Oct. 31, 2018 USD ($)	Jun. 30, 2018 USD ($)	Apr. 30, 2017 USD ($)	Apr. 30, 2017 EUR (€)	Sep. 30, 2015 USD ($)	Sep. 30, 2015 EUR (€)	Mar. 31, 2015 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2006 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2017 EUR (€)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)
Research Agreements
Collaborative arrangement, milestone payments										$ 0	$ 8,712		$ 0
License agreements, upfront payment received											10,000
Eisai | License Agreement
Research Agreements
Period after the date of the first commercial sale of the product for license expiration										10 years
Initial license fee paid									$ 500					$ 400
Additional payments to be made upon achievement of certain clinical and regulatory milestones							$ 22,300
Duke University | License Agreement
Research Agreements
Nonrefundable, non-creditable payment											1,300
Additional payments to be made upon achievement of certain milestones											$ 3,800
Collaborative arrangement, termination period											60 days	60 days
Collaborative Arrangement | 3M Company and 3M Innovative Properties Company
Research Agreements
Funding to purchase capital equipment	$ 9,600
Nonrefundable, non-creditable payment															$ 26,300
Collaborative Arrangement | Ipsen
Research Agreements
Nonrefundable, non-creditable payment					$ 13,000
Additional payments to be made upon achievement of certain milestones					$ 28,700	€ 24.0
Collaborative arrangement, milestone payments			$ 8,700	€ 8.0							$ 8,700	€ 8.0
Royalty rate (as a percent)					5.00%	5.00%
Period after the date of the first commercial sale of the product for license expiration					10 years	10 years
Royalty expense										$ 5,000	600
Collaborative Arrangement | Ipsen | Sublicense Agreement
Research Agreements
Period after the date of the first commercial sale of the product for license expiration					10 years	10 years
Agreement expiration period, period after date of first commercial sale of product					10 years	10 years
Collaborative Arrangement | Ipsen | License Agreement
Research Agreements
Amount awarded to other party		$ 10,000
Settlement interest		800
License agreement, obligation to pay										$ 5,000
Settlement expense								$ 10,800
Upfront payment received		10,000
Aggregate upfront payment received		$ 40,000
Collaborative Arrangement | Eisai
Research Agreements
Nonrefundable, non-creditable payment																$ 1,000
Collaborative Arrangement | Teijin Agreement
Research Agreements
Additional payments to be made upon achievement of certain milestones											40,000
License agreements, upfront payment received											$ 10,000